In an electric power tool using a brushless motor, there is a need to employ a structure for effectively cooling a motor and a switching element, both of which tend to become hot during operation. Japanese Patent Application Publication No. 2009-72880 discloses a brushless motor in which a radiator member is in contact with a switching element to dissipate the heat generated from the switching element.
In the conventional brushless motor, however, electronic components, such as a switching element and the like, and connection portions thereof are arranged on a circuit board in an exposed state. If the brushless motor is employed in an electric power tool, iron particles or water droplets present in the air may adhere to the exposed components or portions, eventually causing short circuit. In case where an air supply-exhaust hole is formed in a housing near the motor in an effort to introduce the air therethrough, enhanced air cooling performance is not compatible with reliable prevention of short circuit caused by the air introduced. In other words, an increase in amount of air introduced through the air supply-exhaust hole may results in an increased possibility of short circuit caused by iron particles or water droplets present in the air introduced.